A Popular Mechanics article published in September 1937 heralded an automotive innovation: the sunroof. “Getting a sun tan while you ride is possible if your automobile is equipped with a sliding roof like that a photographer discovered recently on the streets of an American city,” the magazine said. “The roof slides in a tight seam which prevents rain from entering when it is closed.

Eighty years after the sunroof made its debut atop a Nash Motors model, the humble panel has been eclipsed by another: the moonroof, which first appeared in 1973 on the Lincoln Continental Mark IV. But the terms have become so intermingled that even industry veterans have trouble distinguishing the two.

“These days, there’s not much difference between a sunroof and a moonroof,” said Nelson Ireson, senior editor at Automobile. “It used to be that sunroofs were metal rather than glass, and could open the cabin to the air, while moonroofs were transparent or tinted glass panels that could have a sliding cover and need not, but might slide open. Modern designs are so varied as to defy categorization, with nearly any imaginable variant and combination of opening, sliding, transparent or electronically variable, and panoramic roofs available.”

Eager dealers and glossy new car brochures nowadays seem to use the terms interchangeably to sell a feature, usually optional, that provides some exposure to the elements without the drawbacks of a convertible. “I always just say ‘sunroof’ if a car has a hole in its top,” said Karl Brauer, executive publisher of Kelley Blue Book. “I believe every moonroof is also technically a sunroof but not the reverse.”

In general, a sunroof is a panel – either glass or opaque – in a vehicle’s roof that pops up or slides to the side to let air or light into the cabin. A moonroof is a type of sunroof: a glass panel that slides between the vehicle’s roof and headliner.

For car shoppers, the main question should be not about technical definitions but whether they’re getting the features they want, said Jamie Page Deaton, managing editor of U.S. News Best Cars. “At US News, we just call the feature whatever the manufacturer is calling it,” she explained. “Sunroofs and moonroofs seem to be caught up in an overall automotive trend where old designations are being tested and stretched, which is why we now have four-door coupes and crossover SUVs. No matter what you call things, though, consumers have more choices available to them when they car shop, which is always a good thing.”